Long-term ATAC data supports Arimidex over tamoxifen

Anglo-Swedish drug major AstraZeneca says that new data presented at the 29th annual San Antonio Breast Cancer Symposium confirm that, after five years of adjuvant breast cancer treatment, Arimidex (anastrozole) performs significantly better than tamoxifen across a number of crucial safety and tolerability parameters, including endometrial abnormalities and venous thromboembolic events.

According to the firm, the six-year results from a prospective sub-protocol of the Arimidex, Tamoxifen, Alone or in Combination (ATAC) trial, presented at the Texas, USA, conference, confirm that Arimidex is associated with a third fewer endometrial abnormalities than tamoxifen (27% versus 44%, respectively, p=0.17). These data suggest that, unlike tamoxifen, it does not have a stimulatory effect on the endometrium. These data also support earlier findings from the main ATAC trial, which showed that treatment with tamoxifen led to a significantly higher incidence of vaginal bleeding and a four-fold increase in hysterectomy compared with Arimidex.

The London-headquartered firm noted that the mature data from the ATAC trial confirm that the risk:benefit ratio in early breast cancer continues to favor Arimidex over tamoxifen. It hopes that, as confidence in the drug's efficacy and safety profile builds within the oncology community, so will its potential to be explored in combination with other treatments and as a preventative therapy.